1. Field of the Invention
The present invention relates to a playback apparatus which is suitably used for a usage form in which contents, including video, audio or the like, are read from a record medium where those contents are recorded, and then, the original video, audio (such as music) or data is restored or transmitted to another piece of equipment or a network. It also relates to a playback method and a program product wherein a playback processing program is held by a signal holding medium, which are suitably used for the same usage form.
2. Description of the Related Art
Conventionally, a playback art has been known which has the function of regenerating contents as well as copyright information and restricting the use of the contents. As such a playback art, for example, Japanese Patent Laid-Open No. 2002-112210 specification describes an additional-information embedding apparatus. In that conventional apparatus, additional information is embedded in a video signal. As a more general art, an apparatus or a method has been known in which additional information is embedded in a data part except a video signal. As an example of such an art, there is a hard-disk drive playback apparatus (hereinafter, referred to as the “HDD playback apparatus”) whose main configuration is shown in FIG. 16.
An HDD playback apparatus 900 plays contents which includes a stream and management information. The stream includes a packet group which is obtained by multiplexing a video, audio, or attribute information. The management information is copyright information on the entire stream or information on its configuration. The packet includes a packet header, and a payload which carries a video, audio, data, a caption, or attribute information. The packet header includes information on multiplexing, or the like. It often includes copyright information. In the video, there is included, for example, MPEG2-video, MPEG4-video, or the like. MPEG2-AAC or the like is included in the audio. In the attribute information, there is included, for example, information such as copyright information which is included in a PMT (or program map table) that is defined in a MPEG2-TS, a PAT (or program association table), a SIT (or selection information table), or the like.
The copyright information is information which decides whether or not a permission to make a copy, such as stream recording, should be given. In short, it is information which defines restrictions on copying. For example, there are CopyFree, CopyOnce, and the like. The CopyFree indicates that stream recording can be freely made, and the CopyOnce indicates that stream recording can be made only once. Except for such information, there are also known CopyNoMore which indicates that no more stream recording can be made, CopyNever which indicates that stream recording can never be made, or the like.
The HDD playback apparatus 900 shown in FIG. 16 includes: a playback-mode control section 912; a reading control section 914; a management-information control section 916; a transfer control section 918; a decoder control section 920; a record medium 922; a temporary-storage memory 924; a stream analysis section 926; a decoder 928; and an output control section 930. The record medium 922 is used to record contents. When contents are recorded in the record medium 922, or when they are read from the record medium 922 and played, both a stream and management information are recorded and played. In further detail, when contents are recorded in the record medium 922, the management-information control section 916 generates management information, based on various kinds of information which are included in a stream. Then, it records the management information in the record medium 922. On the other hand, when contents are read from the record medium 922, a stream is read out to the temporary-storage memory 924 by the reading control section 914, and management information is read out to the management-information control section 916 by the reading control section 914.
The HDD playback apparatus 900 plays, in various modes, contents which are recorded in the record medium 922. The playback mode is controlled by the playback-mode control section 912. As the playback mode, there is, for example, a normal playback, a double-speed playback, a quadruple-speed playback, a half-speed playback, a reverse playback, a double-speed reverse playback, a quadruple-speed reverse playback, a half-speed reverse playback, a normal playback or a reverse playback at another speed, or the like.
According to the control by the playback-mode control section 912, the reading control section 914 reads the stream which is recorded in the record medium 922. Then, it stores the stream in the temporary-storage memory 924. For example, at the time of the quadruple-speed playback, the reading control section 914 needs to read the stream at quarter the cycle of the normal playback from the record medium 922 and store it in the reading control section 914. In contrast, for example, at the time of the half-speed playback, the reading control section 914 reads the stream at double the interval of the normal playback from the record medium 922 and stores it in the reading control section 914. According to the control by the playback-mode control section 912, the transfer control section 918 reads the stream which is stored in the temporary-storage memory 924. Then, it sends the stream to the stream analysis section 926.
According to the control by the transfer control section 918, the stream analysis section 926 analyzes the contents of the stream which has been sent from the temporary-storage memory 924. At the lower part of FIG. 16, an example is shown of a part of the stream which is analyzed by this stream analysis section 926. This example shows only a video stream which is included in the stream. Besides, it shows only the fourth and the fifth of a GOP (or group of picture) which is compressed and encoded in an MPEG2 format.
In order to make this description simpler, let's assume that an I-picture, a B-picture and a P-picture are included in each GOP, as shown in the figure. In the stream, copyright information is encoded, simultaneously with the video stream shown in the figure. In the figure, such information is shown under each GOP of the video stream. In the example of the figure, the copyright information from the I-picture of the fourth GOP up to the fifth picture (i.e., the third B-picture) is “A”. On the other hand, the copyright information on the sixth picture and the following picture and all the pictures of the fifth GOP is “B”. Herein, for example, the copyright information “A” represents the “CopyOnce”, while the copyright information “B” represents the “CopyNoMore”. According to the control by the transfer control section 918, the stream analysis section 926 reads, from the temporary-storage memory 924, such a stream which includes the video stream and the copyright information as shown in FIG. 16. Then, it analyzes its contents.
The copyright information which has been analyzed by the stream analysis section 926 is sent to the transfer control section 918. The transfer control section 918 refers to the copyright information which has been analyzed and extracted by the stream analysis section 926. It also refers to the management information which is stored in the management-information control section 916 or copyright information on all the contents which are recorded and managed separately from a video stream, another piece of control information, or the like. Thereby, it creates output control information on this stream.
For example, let's assume that the copyright information which has been encoded at the same time with the video stream is “A” and this “A” represents the “CopyOnce”, and that the present playback mode which is controlled by the playback-mode control section 912 is a normal playback mode. In that case, this stream needs to be overlaid with the copyright information of “CopyNoMore” and outputted from the output control section 930. On the other hand, for example, let's assume that the copyright information which has been encoded at the same time with the video stream is “B” and this “B” represents the “CopyNoMore”. Then, for example, if the present playback mode which is controlled by the playback-mode control section 912 is the normal playback mode, this stream needs to be overlaid with the copyright information of “CopyNever” and outputted from the output control section 930.
For example, let's assume that the copyright information which has been encoded at the same time with the video stream is “A” and this “A” represents the “CopyOnce”, and that the present playback mode which is controlled by the playback-mode control section 912 is the normal playback mode. Even in such a case, if the copyright information on all the contents which are recorded and stored in the management-information control section 916 represents, for example, the “CopyNoMore”, then this stream needs to be overlaid with the copyright information of “CopyNever” and outputted from the output control section 930.
Therefore, if there are both the copyright information which has been encoded at the same time with the video stream and the copyright information on all the contents which are recorded and stored in the management-information control section 916, the transfer control section 918 compares both. Then, it extracts stricter copyright information, and as information for output control (hereinafter, referred to as the “output-control information”), sends it to the playback-mode control section 912. On the other hand, if there is only either of the copyright information which is encoded in the video stream and the copyright information on all the contents which are recorded and stored in the management-information control section 916, there is no need to refer to both. Thus, the transfer control section 918 sends either of the two pieces of copyright information as the output-control information to the playback-mode control section 912. Furthermore, if there is neither of the copyright information which is encoded in the video stream and the copyright information on all the contents which are recorded and stored in the management-information control section 916, the transfer control section 918 makes an output free and sends information to that effect to the playback-mode control section 912.
In addition to the copyright information, if some attribute information which may restrict the use of the contents is encoded and included in the video stream, or recorded and stored in the management-information control section 916, the transfer control section 918 refers to all these pieces of information. Then, it compares and considers them, extracts the strictest condition as the output-control information, and sends it to the playback-mode control section 912. In contrast, depending upon the setting of the transfer control section 918, the transfer control section 918 can extract, for example, the most lenient condition as the output-control information and send it to the playback-mode control section 912. Besides, it is also possible to set some reference, extract the output-control information and send it to the playback-mode control section 912.
Then, the playback-mode control section 912 accepts the output-control information from the transfer control section 918. Sequentially, it compares and considers its contents and the present playback state (e.g., which playback mode is in operation, and a copy or a move). Thereby, it executes output control of this stream in the output control section 930. The operation of the playback-mode control section 912 will be described later in connection with the operation of the output control section 930.
Then, the transfer control section 918 sends the video stream from the temporary-storage memory 924 to the stream analysis section 926. It is sent in the sending timing which corresponds to each playback mode, for example, the double-speed playback, the quadruple-speed playback, the half-speed playback, or the like, or in the sending order of a GOP which corresponds to the reverse playback. For example, at the time of the reverse playback, the transfer control section 918 sends the GOP in reverse numerical order. Then, the stream analysis section 926 executes a stream analysis. According to the order which is applied to each playback mode, it sends each GOP to the decoder 928. Among the streams which have been read out to the temporary-storage memory 924, attribute information is to be analyzed in the stream analysis section 926. On the other hand, presentation data such as a video and an audio is sent to the decoder 928, and then, it is to be decoded.
The playback-mode control section 912 executes control so that the decoder control section 920 controls decoding by the decoder 928. According to the control by the decoder control section 920, the decoder 928 decodes the video stream which has been sent from the stream analysis section 926. The decoding by the decoder 928 differs in each encoding format, for example, an MPEG2, an MPEG4 or another format. In the example of FIG. 16, an MPEG2 is assumed. The stream which has been decoded by the decoder 928 is sent to the output control section 930, and then, it is to undergo output control.
As described already, for example, the final output-control information is created by the transfer control section 918 from: (a) copyright information which is encoded in a video stream, (b) copyright information on all contents which are recorded and stored in the management-information control section 916, or (c) information for controlling an output of some stream other than copyright information. Then, that information is sent to the playback-mode control section 912. Next, the playback-mode control section 912 compares and considers the information which has been sent from the transfer control section 918 and the present playback state which is managed by the playback-mode control section 912 itself. As a result, it overlays a stream to be outputted with each piece of copyright information, for example, “CopyNever”, “CopyOnce”, “CopyNoMore”, or the like. and outputted from the output control section 930. Then, it allows the output control section 930 to output the stream.
As described above, based on copyright information on contents which are recorded in the record medium 922, the conventional HDD playback apparatus 900 plays a stream in the contents and executes output control for using the stream.
However, in the conventional HDD playback apparatus 900, it is the stream analysis section 926 that analyzes copyright information which is encoded in a video stream. In the transfer control section 918, the copyright information which has been analyzed and extracted by this stream analysis section 926 is collated with another piece of copyright information, or each of various pieces of information which relate to output control. Then, the final output-control information is created. Sequentially, that information is sent to the playback-mode control section 912. In the playback-mode control section 912, it is compared with the present playback state (e.g., a copy, or not a copy but a move). As a result of the comparison, the playback-mode control section 912 allows the output control section 930 to execute output control. This can easily cause temporal mismatching. Therefore, it will be difficult to reflect each picture or frame unit of copyright information which has been analyzed by the stream analysis section 926, precisely in a frame or picture unit, in output control by the output control section 930. This disadvantage is conspicuous in the case where the playback mode is a reverse playback (e.g., a playback which is referred to as a “reverse slow playback”, and the like), or a normal or reverse fast playback which is executed by using only an I-picture.
For example, at the time of the reverse slow playback, a video stream which includes far more pictures than those of a video stream that is outputted from the output control section 930 is analyzed by the stream analysis section 926. Then, copyright information is extracted. Consequently, it is difficult to accurately decide which piece of copyright information is copyright information that corresponds to each picture of a video stream which is outputted from the output control section 930. In other words, it is more difficult to precisely extract output control which corresponds to each picture of a video stream which is outputted from the output control section 930 from copyright information on each picture, and executes the output control synchronously.
FIG. 17 shows a simplified example of the flow of the video stream and the copyright information at this time. FIG. 17 illustrates a case in which the reverse slow playback is executed at half the normal speed. In this example, first, the fourth GOP is requested by the transfer control section 918. Then, it is read from the temporary-storage memory 924 and sent to the stream analysis section 926. The stream analysis section 926 analyzes the sent stream and picks up copyright information. In addition, it sends video-stream data to the decoder 928.
Next, after double the processing cycle at the time of the normal playback elapses, the third GOP is sent from the temporary-storage memory 924 to the stream analysis section 926. However, in some cases, during a vacant period of time which is equivalent to one processing cycle of the normal playback, the following fifth GOP may be sent from the temporary-storage memory 924 to the stream analysis section 926. This fifth GOP is a GOP which does not require the reverse slow playback, and thus, it is not supposed to be outputted from the decoder 928. But the stream analysis section 926 often picks up copyright information and sends it the transfer control section 918.
Therefore, as shown in the right-hand end of FIG. 17, the flow of the detected copyright information is A-B-C-D-A-B-E-D-A. However, the video to be actually played is a video which is obtained by arranging each picture of each GOP from the fourth to the second in their reverse order. Hence, the copyright information on the stream to be played needs to be B-A-D-E. Nevertheless, the flow of the detected copyright information makes it extremely difficult to choose the necessary copyright information.
In contrast, for example, in the case where the fast playback is executed using only the I-picture, not the entire stream but only a part if the stream is frequently transferred from the temporary-storage memory 924 to the stream analysis section 926. This presents another disadvantage in that copyright information which is included in attribute information in a stream may not be transferred, so that the necessary copyright information cannot be detected.
In addition, since the decoder 928 has a limited storage capacity, in some cases, the whole GOP cannot be stored in the decoder 928, depending upon the data size of a GOP. In such a case, at the time of a general reverse playback including the reverse slow playback, in order for the decoder 928 to complete the decoding of the whole GOP, it has to repeatedly send the same GOP to the decoder 928. If there is a GOP to be sent in the temporary-storage memory 924, it may also be reused. On the other hand, unless there is such a GOP, it may also be read into the temporary-storage memory 924 and sent out. This causes the same copyright information to be repeatedly extracted from the same GOP. As a result, there is disadvantage in that the necessary copyright information cannot be properly selected.